Apparatus for chloridizing aluminum-base alloys



1943- A. SMITH, JR, EI'AL 2,447,672

APPARATUS FOR CHLORODIZING ALUMINUM-BASE ALLOYS Filed Nov. 20. 1944Patented Aug. 24, 1948 APPARATUS FOR cnmarmzmo mm. HUM-Bass ALLOYSAlbert A. Smith, In, Metuehen, and Raymond A.

Quadt, Woodbridge, N. 1., alslgnor's to Amer-i can smelting and RefiningCompany New York, N. Y., a corporation of New Jerseyv ApplicationNovember :0, 1944, Serial No. 564,209;

l This invention relates to the refining of aluminum and, moreparticularly, to the chloridization of aluminum-base alloys to effectthe removal of magnesium.

It has been proposed in the past to bubble halogen gas through a moltenbath of aluminum in order to remove dissolved gases and suspended solidimpurities, such as dirt, oxides, nitrides, carbides, etc., therefrom;further, it has been proposed to conduct the de-gassing of aluminum andaluminum-base alloys by chlorine in an atmosphere of dry air.

More recently, it was suggested that magnesium might be selectivelyremoved from aluminum alloys .by treating such alloys with chlorine.However, repeated attempts to carry the suggestion into commercialpractise met with failure both as regards effecting properchloridization and in obtaining a satisfactory casting of the refinedmetal.

The present invention provides certain improvements in an apparatuswhich establishes the selective chloridization of magnesium fromaluminum-base alloys as a, truly commercial operation.

Although the novel features which are believed to be characteristic ofthis invention will be particularly pointed out in the claim appendedhereto, the invention itself, as to its objects and advantages, and themanner in which it may be carried out, may be better understood byreferring to the following description taken in connection with theaccompanying drawing, forming a part thereof, in which Fig. 1 is a viewin elevation, partly in section,

' of apparatus embodied by the invention and suitable for practicing theprocess thereof; and

Fig. 2 is an enlarged view of a portion of the apparatus'shown in Fig. 1showing, in section, the tube for introducing the chlorine gas into themelt and the mounting of the tube in the furnace wall.

Like reference characters denote like parts in the two figures of thedrawing. In the drawing, ll indicates a furnace of the reverberatorytype which may be equipped with IClaim. (cu zoo-s4) in Fig. l, the tubeI3 is of such length that its discharge end extends to a positionadjacent the furnace hearth.

The tube I! is made of a suitable refractory material, for example,silicon carbide, quartz,

graphite or the like, that is resistant to the corrosive action ofgaseous chlorine. It has been found that a very satisfactory tube can beprovided by drilling a .5 to 35-inch diameter hole centrally andlongitudinally of a 3.25-inch dense graphite electrode of desiredlength. The upper and outer end of the graphite tube 13 is connected toa pipe section I by means of a reducer pipe coupling i5 threaded on theend of the graphite tube. To assure a gas-tight point the threads arefilled with a mastic composed of powdered graphite and light machine oiland, after screwing the coupling on tightly, the joint is packed withgraphite mastic as indicated at I, Fig. 2.

To preclude vibration or whipping action of the 1 tube l3 during use, itis firmly mounted by providing a silicon carbide sleeve i1 extendingdiagonally through the furnace wall from'inner wall opening 2! to outerwall opening 22. It will be observed that the inner wall opening II iswell below the surface of the'melt l2 thereby pre-, eluding acceleratedoxidation of the tube I! by direct action of the furnace flame fromburner i'i,

while the outer wall opening 22 is well above themelts of thecomposition for the'treatment of which the present invention isparticularly applicable, i. e., melts analyzing up to 2% magnesium, thefurnace may be provided with a plurality of tubes I! if deemed desirableor necessary.

As illustrated in Fig. 1, a steel cylinder 25 containing liquid chlorineis supported on a suitable scale means equipped with a weight indicatingdial hand 21. A cradle structure II is provided on the scale means 2Bfor retaining the liquid chlorine tank 28 on its side with one endsiightly raised. Pipe means II, 3| lead from the liquid chlorine tank25, through needle valve N 3 to a vaporizer comprising copper coil 32immersed in heated water bath 33, and thence through globe valve 33,nippled section 33 and T-pipe fitting 36' to pipe i4 and refractory tube13. A gate chlorine gas. Conducting the chloridization in this mannerwith a tube l3 having a .5-inch diameter bore, no difficulty has beenencountered in introducing chlorine into melts at a rate of from 100 to200 pounds per hour up to several times that figure except for anincreased tendency toward aluminum chloride formation at the higherrates.

The advantages attending the use of the invention will be readilyapparent from the following actual commercial runs. In the firstinstance, a melt of 23 tons of aluminum-base scrap materials wasestablished at about 730 C. in a reverbatory furnace as hereinbeforedescribed. The

depending somewhat upon the constituents of the particular melt. Whileslightly higher temperatures can be tolerated, they should not exceed anupper maximum of 850-900 C. This is an important consideration as it hasbeen found that temperatures above this maximum range invariably invitenot only improper chloridization but imperfections in the cast metal aswell.

Having established the melt at the proper temperature, valve 39 isopened wide and needle valve 34 slowly opened to admit liquid chlorinefrom cylinder 25 into the coil section 32 where the chlorine isvaporized and from whence the gaseous chlorine passes through valve 33,'pipe l4 and downwardly through tube I 3 into the melt I! at a pointimmediately above the hearth of the furnace. By introducing the gaseouschlorine in this manner, it has been found that sufilcient agitation andcirculation of the metal results to selectively chloridize the magnesiumto magnesium chloride which floats on the melt and renders itunnecessary to provide for mechanical agitation. The weight of chlorineintroduced into the melt can be readily obtained by observing therelative change in position of the dial hand 21.

Liquid chlorine supply cylinder 25 is preferably located in a relativelycool place, that is. a location where it will not be subjected totemperatures appreciably above room temperature. 0n the other hand, thevaporizing unit is preferably located in an environment of highertemperature,

--e. g., adjacent the outer wall of the furnace, as

an aid in providing warmth to the water bath 33 for insuring completevaporization of the chlorine passing into the tube i3. As'a simplecontrol measure for plant operation, it has been found effective to openthe needl valve 34 sumciently to provide a flow of chlorine through coil32 at such rate that no frost forms between the needle valve and thevaporizing unit but that frost does develop on the pipe coupling i5.Operating in this manner, the controlled fiow of chlorine is such thatno liquid chlorine enters the melt; additionally, the coupling l5, pipe14, etc., may be made of cast iron as such operation renders them immuneto accelerated corrosive attack by the melt analyzed originally 0.75%magnesium and was treated with 1880 pounds chlorine over a twohourperiod. The cast product was sound and contained only 0.02% magnesium.In a similar run, a 24.6 ton melt analyzing 1.1% magnesium was broughtto a temperature of about 705. C. and treated with 2610 pounds chlorineduring a four-hour period. Sound metal ingots were cast analyzing only0.01% magnesium.

The present application is a continuation-inpart of applicants priorapplication Serial No. 469,544, filed December 19, 1942, now abandoned.

What is claimed is:

Apparatus for refining metal such as an aluminum-magnesium mixture toremove magnesium from the aluminum in the form of magnesium chloridewhich comprises a furnace for maintaining a molten bath of said metal,means for internally heating said furnace to melt said metal, a tank forliquid chlorine, a temperature controlled chlorine vaporizer, a conduitconnecting said tank and vaporizer to carry liquid chlorine from saidtank, a valve in said conduit ahead of said vaporizer to control therate of flow of chlorine into said vaporizer, a duct through a ALBERT A.SMITH, JR. RAYMOND A. QUAUI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Messner Oct. 3, 1939 Number

